1. Field of the Invention
The invention relates to a recording and reproducing device having recording means which includes at least two magnetic heads, mounted on a rotatably supported head disc and having Z different azimuth angles, for the recording of recording data in helical recording tracks on a magnetic tape, a part of the recording data being recordable as information data in an information data recording area of each helical recording track, this recording area being always the same as regards its position in a helical recording track, and having reproducing means for reproducing at a maximum N-fold reproducing speed, information data recorded on a magnetic tape, each of the at least two magnetic heads being capable of scanning a helical reproducing track which traverses N helical recording tracks.
2. Description of the Related Art
Such a recording and reproducing device of the type defined in the opening paragraph is known from International Patent Application WO 98/34225, corresponding to U.S. patent application Ser. No. 09/155,682, filed Oct. 2, 1998, and takes the form of a video recorder. The known video recorder has recording means which enable recording data, including picture, sound and information data, to be recorded in helical recording tracks on a magnetic tape of a magnetic-tape cassette. For this purpose, the recording means comprise a scanner having a head disc on which two magnetic heads, a magnetic head A and a magnetic head B, are mounted so as to be rotationally drivable. Head gaps of the magnetic heads A and B have different azimuth angles (Z=2) in order to reduce crosstalk from recording data recorded in adjacent tracks during the reproduction of the recording data. Due to the different azimuth angles, recording data recorded in a helical recording track by the magnetic head A can be reproduced only by the magnetic head A.
In order to reproduce recording data recorded on a magnetic tape, the known video recorder further comprises reproducing means which includes the two magnetic heads A and B. The reproducing means reproduces recorded recording data at a normal reproducing speed, the transport speed of the magnetic tape during reproduction being the same as during the recording of recording data, from a helical reproducing track which is scanned by a magnetic head A or B covering only one helical recording track. The reproducing means also reproduces recording data at a multiple reproducing speed which is not more than 24 times as high (N=24), the transport of the magnetic tape being effected at a multiple not greater than 24 times the speed used for the recording of recording data, from a helical reproducing track scanned by a magnetic head A or B partly covering a maximum of 24 helical recording tracks at a time. In the case of a 24-fold reproducing speed, 24 recording areas of 24 helical recording tracks being traversed are scanned, recording data which have been recorded for reproduction at the 24-fold reproducing speed being reproduced from 12 of the 24 recording areas, so-called trick-play recording areas. Such recording data recorded in trick-play recording areas may include trick-play data which contain picture information and sound information, as well as additional information, for example, a summary of the content of a television program which can be reproduced from the magnetic tape at the normal reproducing speed.
The know video recorder is adapted to record additional information, to be reproduced at a multiple reproducing speed which is maximum N times as high, in an each time similar information data recording area, i.e., a so-called subcode recording area, of each helical recording track. During a reproduction at the N-fold reproducing speed, a helical reproducing track of the magnetic heads A and B alternately scans the subcode recording area of every Nth helical recording track. Since, as a result of the different azimuth angles, the magnetic heads A and B can only reproduce recording areas of every second helical recording track that is scanned, information data can be reproduced from every (2*N)th helical recording track of the subcode recording area at an N-fold reproducing speed.
When additional information is to be recorded as additional data by means of the known video recorder and the additional data are so extensive that the additional data cannot be recorded as additional information in an information data recording area of a helical recording track, the additional data should be divided into a plurality of, for example, K partitions of information data, these partitions being recorded in K information data recording areas. When the additional data are to be reproduced at several reproducing speeds up to a maximum N-fold reproducing speed, two possibilities of recording the K partitions of information data are known.
In accordance with the first known possibility, the first of the K partitions of information data is recorded N times in the information data recording areas of N helical recording tracks, and subsequently, the second of the K partitions of information data is recorded N times in the information data recording areas of N helical recording tracks until, eventually, the K partitions of information data have been recorded in total, in K*N information data recording areas of K*N helical recording tracks. This has the drawback that also at the normal reproducing speed, information data must be reproduced from basically all the K*N helical recording tracks in order to reproduce all the information data forming the additional data.
In accordance with the second known possibility, all the information data forming additional data are recorded for each desired reproducing speed in information data recording areas in helical recording tracks which depend on the desired reproducing speed. For example, for reproduction at the N-fold reproducing speed, as explained hereinbefore, information data are recorded in the information data recording areas of every (2*N).sup.th helical recording track. For reproduction at an (N-3)-fold reproducing speed, the same information data are recorded in the information data recording areas of every [2*(N-3)].sup.th helical recording track. This has the drawback that there may be overlaps when different information data for different reproducing speeds are to be recorded in the same information data recording area of the same helical recording track.